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Body Fat Percentage Estimator

Estimate your body fat percentage using the US Navy circumference method — widely used by military and fitness professionals. Just three body measurements required. Free, no signup.

Estimate Body Fat %
📏 How to measure accurately:
Height: stand straight without shoes
Neck: just below the larynx (Adam's apple), slightly tapered
Waist: at the narrowest point (men) or at the navel (women)
Hip: at the widest point around the buttocks (women only)
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body fat
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CategoryMenWomen
Essential Fat2–5%10–13%
Athlete6–13%14–20%
Fitness14–17%21–24%
Average18–24%25–31%
Obese25%+32%+
Your body composition estimate:
Fat mass
Lean mass

How the US Navy Body Fat Method Works

The US Navy circumference method uses a mathematical formula based on body measurements to estimate body fat percentage. It was developed by the US Naval Health Research Center and is used in military fitness assessments.

The formulas are:

Men: %BF = 86.010 × log10(waist-neck) − 70.041 × log10(height) + 36.76 Women: %BF = 163.205 × log10(waist+hip-neck) − 97.684 × log10(height) − 78.387 (all measurements in cm)

Accuracy and limitations

The Navy method has an error margin of approximately ±3–4% compared to DEXA scan (the gold standard). It's useful for tracking trends over time and is more practical than skinfold calipers for most people. It tends to overestimate body fat in very lean individuals and underestimate in those with unusual fat distribution.

More accurate methods

  • DEXA scan: Gold standard, accurate to ±1%. Available at hospitals and some fitness facilities.
  • Hydrostatic weighing: Very accurate but requires full submersion in water — rarely accessible.
  • Skinfold calipers: Accurate when performed by a trained technician using a multi-site protocol.
  • BIA scales: Consumer smart scales using bioelectrical impedance. Convenient but affected by hydration levels — can vary by 4–5% depending on when you measure.

Frequently Asked Questions

What is a healthy body fat percentage?
For men: 10–20% is generally considered healthy (athletic 6–13%, fitness 14–17%, average 18–24%). For women: 18–28% is generally healthy (athletic 14–20%, fitness 21–24%, average 25–31%). Women naturally carry more essential fat than men for hormonal and reproductive health.
Is body fat percentage better than BMI?
For assessing health risk, body fat percentage is generally more informative than BMI because it directly measures fat tissue rather than total weight. A muscular athlete may have a high BMI but low body fat (healthy), while a sedentary person may have a normal BMI but high body fat (unhealthy). However, BMI has far more clinical research behind it for population-level health risk prediction.
How often should I measure body fat?
Monthly measurements are most useful for tracking progress. More frequent measurements introduce noise — daily fluctuations from hydration, digestion, and hormonal cycles can create apparent changes of 1–3% that aren't real fat changes. Always measure at the same time of day (morning, before eating) for consistency.